Asymmetric Formal [3+2] Cycloaddition Reactions of 3-Isothio­cyanato Oxindoles: an Update

Abstract

3-Isothiocyanato oxindoles are a class of important building blocks which have been widely used in the synthesis of structurally diverse enantio-enriched spirooxindoles. In this short review, it is attempted to cover the recent synthetic aspects of 3-isothiocyanato oxindoles participated cascade cyclizations in the last few years (i.e., from 2017 to 2022), with an emphasis on formal [3+2] cycloaddition reactions.

Trimethylindolenines as C–N synthons for the assembly of spiro[oxindole-thioxoimidazolidine-indoline] hybrids in formal [3+2] cycloadditions

“…3-Isothiocyanato oxindoles, 8 pioneered by the Yuan group in 2011, 8 a have been widely employed as extremely efficient and versatile cascade reagents for the synthesis of corresponding spirooxindoles through a formal [3+2] cycloaddition reaction with electron-deficient substrates. Despite these achievements, however, there are no reports on the formal [3+2] cycloaddition reaction of 3-isothiocyanato oxindoles with trimethylindolenines for access to a series of diverse penta/hexacyclic spirooxindole scaffolds (Scheme 1a), although they are potentially useful in medicinal chemistry.…”